T/F The mode of action of xanthines is unclear.
True; may be related to antagonism of adenosine receptors.
Why is it necessary to titrate the dosage of thoeophylline to the individual?
The rate of metabolism varies by each person.
T/F Theophylline has a wide therapeutic margin because each individual metabolizes it differently.
False. Each individual metabolizes it differently, but the therapeutic margin is still narrow. Blood levels of theophylline are affected by many factors, which can either increase or decrease the amount of drug in the body.
Theophylline is considered in the treatment of asthma ONLY if what two other types of drugs fail to control symptoms?
β agonists and antiinflammartories
In COPD, what are two effects (non-bronchodilating) for which theophylline is valuable?
Ventilatory drive stimulation and enhanced respiratory muscle (diaphragm) function
Why do COPD guidelines suggest the use of inhaled β agonists and inticholinergics over theophylline?
B/c of the side effects of theophlline.
What is the definition of alkaloids?
Group of alkaline substances taken from plants, which react with acids to form salts, e.g. theophylline
Why is theophylline NOT the first-line drug for asthma and COPD?
It has a relatively weak bronchodilating effect compared to β agonists.
Therapeutic action of theophylline action may be by : (2)
1) Stimulation of ventilatory drive
2) direct strengthening of the diaphragm.
What type of theophylline is indicated for maintenance (step 2) of mild persistant asthma in patients 5 yrs and up?
Sustained release theophylline.
In step 3, with patients 5 yrs and up, what drug combination may be used for maintenance treatment of asthma?
Sustained release theophylline with inhaled corticosteroid (ICS)
Compare effects of caffeine and theophylline on:
1) CNS stimulation
2) Cardiac stimulation
3) Smooth muscle relaxation
4) Skeletal muscle relaxatoin
1) CNS stimulation: Caff +++ Theo ++
2) Cardiac stim: Caff + Theo +++
3) Smooth muscle relaxation Caff + Theo +++
4) Skeletal muscle relaxation Caff +++ Theo ++
5) Diuresis Caff + Theo +++
The standard with which salts of theophylline are compared is:
anhydrous theophylline. Anhydrous theophylline is 100% theophylline.
T/F Salts of theophylline, such as oxytriphylline are 100% theophylline by weight.
False. Oxytriphylline is only 64% pure theophylline.
Name 3 proposed theories of activity to explain the mechanism of action of xanthines.
1) Inhibition of phosphodiesterase
2) Antagonism of adenosine
3) Catecholamine release
What is the effect of an increase in cAMP on bronchial smooth muscle?
Relaxation of bronchial smooth muscle.
T/F Theophylline is a selective inhibitor of cAMP specific phosphodiesterase (PDE), having a synergistic effect on bronchial smooth muscle.
False. Theophylline is a weak and noselective inhibitor of cAMP-specific PDE.
Adenosine stimulates A-1 and A-2 receptors. What is its effect on each of these?
A-1 receptor stimulation inhibits cAMP.
A-2 receptor stimulation increases cAMP.
Why does enprofylline contradict the antagonism of adenosine theory?
Enprofylline is about 5x more potent than theophylline for relaxing smooth muscle, yet it lacks sufficient attachment at the nitrogen-1 position to be able to provide adenosine antagonism.
What is the formula to calculate an equivalent dose of a theophylline salt to pure theophylline?
100mg (100% theophylline)/ salt % = equivalent dose of salt (do not need to use decimal point b/c you are dividing % into %)
T/F Dyphilline is another name for theophylline.
False. Dyphilline is a derivative of theophylline, but it is not theophylline.
A patient has a theophylline serum level of 10 - 12μg/mL. If you increase his dosage to reach a serum level of 15 μg/mL, what effect would you expect to see on his FEV1?
Very little or none. Above a serum level of 10 - 12 μg/mL, the improvement in FEV tends to flatten out.
Compared to the therapeutic effects of theophylline, the toxic effects tend to _______________ within the therapeutic serum level of 10 - 20 μg/mL.
For rapid theophyllilzation, the patient may be given an oral loading dose of 5 mg/kg only if.....
he was not receiving theophylline previously.
Why should lean body weight be used to calculate theophylline doses?
B/c theophylline does not distribute into fatty tissue.
After a morning dose of sustained release theophylline, when is the appropriate time to test serum level?
5 - 9 hours
List 6 gastrointestinal side effects seen with theophylline?VANDAG:
List 4 cardiovascular sede effects of theophylline?STAPH
Theophylline is metabalized in the ______________ and eliminated via the ________________.
Theophylline has an additvie effect when combined with _______________ and may be used when treating patients with ___________ and _______.
β agonists; asthma; COPD
What effect would theophylline be expected to have on neuromuscular blocking agents (pancuronium and atracurium)?
Theophylline can reverse the paralyzing effect of these drugs. This is important when paralyzing patients with severe asthma in order to give ventilatory support.
List factors that can increase blood levels of theophylline.ABCC & CHP
β blocking agents
Calcium channel blockers
Congestive heart failure
List 4 factors that can decrease blood levels of theophylline.CBIB
Theophylline has been relegated to the level of a second or third line drug for ____________ only after ______________ and __________________ ______________ fail to control symptoms.
asthma; β agonists; anti-inflammatory therapy
In COPD,2 useful non-bronchodilating effects of theophylline are ____________________ _______________ stimulation and enhanced ___________________ muscle function.
ventilatory drive; respiratory
What effect is theophylline thought to have on respiratory muscle contractility?
Increased. This increase may inhibit or reverse muscle fatigue and subsequent ventilatory failure.
T/F Theophylline can increase phrenic and peripheral nerve activity for a given level of chemical stimulus.
False. It is only known to increase PHRENIC nerve activity, not peripheral nerve activity.
Theophylline can ___________ cardiac output, _______________ pulmonary vascular resistance, and ______________ myocardial muscles perfusion in ischemic regions.
Increase; decrease; improve.
In regards to blood brain barrier, why is caffeine preferable to theophylline?
Caffeine more readily penetrates the blood brain barrier.
T/F Caffeine more readily penetrates the blood brain barrier, but theophylline offers simpler dosing regimens and has fewer side effects.
False. Caffeine offers simpler dosing regimens and has fewer side effects than theophylline.
Caffeine citrate is a standard preparatioin of caffeine that can be administered ________ or ______.